1. Field of the Invention
The present invention relates to a medical device for delivering a substance to a vascular lumen. More specifically, the present invention relates to a catheter for delivering a therapeutic substance to a location within a physiological lumen and adjacent tissue/vascular structure.
2. Relevant Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress the atherosclerotic plaque of the lesion against the inner wall of the artery to dilate the lumen. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient""s vasculature.
Restenosis of the artery commonly develops over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. Restenosis is thought to involve the body""s natural healing process. Angioplasty or other vascular procedures injure the vessel walls, removing the vascular endothelium, disturbing the tunica intima, and causing the death of medial smooth muscle cells. Excessive neoinitimal tissue formation, characterized by smooth muscle cell migration and proliferation to the intima, follows the injury. Proliferation and migration of smooth muscle cells (SMC) from the media layer to the intima cause an excessive production of extra cellular matrices (ECM), which is believed to be one of the leading contributors to the development of restenosis. The extensive thickening of the tissues narrows the lumen of the blood vessel, constricting or blocking blood flow through the vessel.
To reduce the chance of the development of restenosis, therapeutic substances are administered to the treatment site. For example, anticoagulant and antiplatelet agents are commonly used to inhibit the development of restenosis. In order to provide an efficacious concentration to the target site, systemic administration of such medication often produces adverse or toxic side effects for the patient. Local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery, thus, produces fewer side effects and achieves more effective results.
One commonly applied technique for the local delivery of a therapeutic substance is through the use of a medicated, implantable prosthesis, one example of which includes a stent. A stent coated with a polymeric carrier, which is impregnated with a therapeutic substance, can be deployed at a selected site of treatment. The polymeric carrier allows for a sustained delivery of the therapeutic substance. A disadvantage associated with the use of medicated stents is that the quantity of the substance that can be impregnated in the polymeric carrier is limited. In order to increase the capacity of the polymeric carrier, the amount of polymeric material employed, and in effect the thickness of the coating must be increased to accommodate the quantity of the substance used. An increase in the profile of the coating significantly limits the applications for which the stents can be used.
One technique for the local delivery of a therapeutic substance into the tissue surrounding a bodily passageway is disclosed in U.S. Pat. No. 5,464,395, to Faxon et al. Faxon et al. discloses a catheter including a needle canula slidably disposed in a needle lumen and a balloon, which is coupled to the distal end of the catheter. When the balloon is inflated the needle lumen is brought into close engagement with the tissue and the needle canula can be moved between a position inboard of the catheter distal surface and a position where the needle canula is projected outboard of the catheter to deliver the therapeutic substance to the tissue.
It has been observed, that in most instances the inflation and deflation of the balloon causes the needle lumen to form a tortuous pathway, which the needle canula must traverse to reach the tissue. Unfortunately, under these conditions the needle canula can become stuck in the pathway, such that it cannot be advanced. For example, the sharp tip of the needle canula can gouge, become lodged in, or puncture the catheter wall. Curving the tip of the needle may help to prevent some damage, but it can require that the needle lumen be made undesirably larger to accommodate the curved needle tip and may result in inconsistent needle engagement with the tissue.
The present invention provides a substance delivery apparatus which can be used to provide local drug therapies to a diseased physiological lumen, for example, to prevent or treat arterial restenosis and to promote angiogenesis response in the ischemic heart. A catheter assembly is provided having a balloon disposed at the distal end thereof. The balloon is capable of being inflated to selectively dilate from a collapsed configuration to an expanded configuration. The balloon is also capable of being deflated after inflation to return to the collapsed configuration or a deflated profile. A therapeutic substance delivery assembly, which can include a needle disposed in delivery lumen, is provided on the catheter assembly for allowing a therapeutic substance to be delivered through the needle and injected into a tissue of the physiological lumen. The delivery lumen defines two sections created as a bend region forms between the sections, as one section moves/rotates relative to the other section. The movement of one section relative to the other section is generally from a first position towards a second position in response to the balloon being inflated from the collapsed configuration to the expanded configuration. The delivery lumen is capable of moving from the second position back towards the first position when the balloon is being deflated.
In accordance with the present invention, a deflector, such as a thin metallic ribbon member, can be positioned along an inside wall of the delivery lumen. The deflector can be positioned, such that as the bend region forms caused by the movement of the sections, the deflector bends to rest on the outside curvature of the bend region. The needle is inserted into the delivery lumen and is urged distally to travel through the bend from a first position, where the needle is retracted within the delivery lumen, to a second position, where the needle extends a distance out from an opening in the delivery lumen.
As the needle travels through the bend region, the ribbon member allows the needle tip to bounce or be deflected off the wall of the delivery lumen, allowing the needle to travel through the bend without puncturing, gouging, or otherwise damaging the wall of the delivery lumen. Since the ribbon member can be made relatively small, the catheter track performance is not compromised. Advantageously, using the ribbon member avoids the need to modify the tip of the needle, thus maintianing a low catheter profile and a consistent needle engagement with the physiological lumen tissue.
These and other features and advantages of the present invention will be more readily apparent from the detailed description of the embodiments, set forth below, taken in conjunction with the accompanying drawings.